The present invention deals with disc drives. More specifically, the present invention deals with limiting undesirable shut down of a disc drive due to undesirable increases in integrated circuit temperature.
A typical disc drive includes one or more discs mounted for rotation on a hub or spindle. A typical disc drive also includes one or more transducers supported relative to surfaces of the discs in the disc drive to read information from, and write information to, the discs. The transducers along with any air bearings associated therewith are collectively referred to as a data head. A drive controller is conventionally used for controlling the disc drive system based on commands received from a host system. The drive controller controls the disc drive to retrieve information from the disc and to store information on the disc.
An actuator operates within a servo system and typically includes an actuator arm that supports a flexure or flexure assembly which, in turn, supports the data head. The actuator moves the data head radially over the disc surface for track seek operations and holds the transducer directly over a track on the disc surface for track following operations.
Information is typically stored on the discs by providing a write signal to the data head to encode information on the surface of the disc representing the data to be stored. In retrieving data from the disc, the drive controller controls the actuator so that the data head flies above the disc, sensing the information on the disc, and generating a read signal based on that information. The read signal is then decoded by the drive controller to recover the data represented by the information stored on the disc, and consequently represented in the read signal provided by the data head.
In some current disc drives, the servo system includes a voice coil motor (VCM) for moving the transducer or data head relative to the tracks on the disc. The disc drive also includes a spindle motor for driving rotation of the rotatable discs in the disc drive. Historically, power has been provided to these two motors using discrete power transistors. However, these power transistors can be integrated into the integrated circuit which switches the power transistors to energize, and deenergize, the voice coil motor and spindle motor.
When all of the power transistors (which in the past have included up to ten individual transistors) are concentrated inside one integrated circuit, the power density of this integrated solution is higher than that found under former solutions with discrete amplifiers. This is because the total power which was previously distributed across ten or more devices is now concentrated into one physical component. Therefore, the junction temperature of the integrated circuit can become problematic, particularly in high performance products. For example, all semiconductors have a maximum reliable operating temperature. Operating the device at or above the reliable operating temperature limit can, and likely will, result in several undesirable behaviors, such as degraded performance, increased power losses, and premature failure.
Prior attempts to deal with the high power density of a totally integrated amplifier used temperature sensors to indicate when the device maximum junction temperature had been reached. This generated a high temperature trigger event. Upon the high temperature trigger event, the disc drive controller would either disable the actuator voice coil amplifier or even turn off the disc drive. In either case, the disc drive was no longer available to save or recall data.
Embodiments of the present invention address one or more of these and other problems, and offers advantages over the prior art.
Embodiments of the present invention are used to control a disc drive having at least one disc and a transducer positionable relative to the disc by a motor. The motor receives energization through at least one power switch integrated on a semiconductor circuit. Temperature of the circuit is sensed proximate the power switch. A threshold temperature signal is provided which is indicative of whether the sensed temperature meets one of a plurality of different threshold temperatures. The power switch is controlled in one of a plurality of different control modes based upon the threshold temperature signal.